Process for the decomposition of diolefin monosulphones



- or the like,

reacting pipe lene with 80:, and freed oi poLvmeric products by precipitation irom water solu- Patented July 31, 1945 PROCESS FOR THE DECOMPOSITION 0! DIOIHIN'MONOBULPHONES Frederick E; Frey and'liarold J. Hcpp, Bartlesville, Okla, assignors to Phillips Petroleum Company, a corporation of Delaware Original-application Deoemberlil, 1e41, sen-nu No.

1944. Serial No. 533,936

This invention relates to a process for decomposing aliphatic .coniugated diolefln monoculphones for the recovery of the diolefln contained therein.

. Aliphatic conjugated dioleiins, such as butadiene, isoprene, piperylene, and the like, may be separated from mixture with other hydrocarbons by reacting with sulphur dioxide under conditions such as to prevent reaction of monooleflns with sulphur dioxide and also to prevent formation of polymeric sulphon'es (P 7 111? phones) oi high molecular weight from the dioleflns. Thus the reaction may be carried out at low temperatures in the presence or inhibitors such as hydroquinone, pyrogallol, phenylbeta-naphthylamine and the like, or at relatively high temperatures, say 100 to 180 C. in the absence of catalysts or inhibitors.v .In either case the principal product formed is the aliphatic conjugated dioletin monosulphone with minor amounts or, or no, polymeric sulphonesand vhydrocarbon polymers. The 'diolefln monosulphone is' characterised by its solubility in water and common organic solvents, and by the fact that upon heating it is decomposed into its. compo- The monosiilphone may be recovered i'rom other materials in the reaction mixture such as unreacted hydrocarbons and sulphur dioflde .by any suitable means such as distillation, ex-

tractiometc.

The recovered monosulphone may be decom- Divlded and this application May 3,

' 3 ohm (Cl. zoo-481.5)

and sulphur dioxide stopped and the flask was allowed to ml. 2.9 g. of a black, tarry material remainedintheilask. Inacommeicialinstallation such tarry products are distributed over the inner surfaces of the apparatus, steam or other heating coils. and require frequent cleaning which requires discontinuance oi operation, involves excessive labor and other charges, and prevents operation in a continuous manner.

The principal object of the present invention is to provide an improved process for electing decomposition of aliphatic conjugated diolefln monosulphones. Another, object is to provide a process in which better control of temperature isreadily obtained. a

A further object is to provide a processior decomposing such monosulphones. wherein the deposition or tarry or otherinsoluble material in the decomposition acne is substantially or entirely avoided.

Another object is to minimise the loss of diolefln'by' polymerisation and/or poLvsulphone formation during the decomposition step.

Another object isto provide a process more adapted to continuous operation.

Numerous other objects will hereinafter aP- Inthe accompanying'drawing: Pigs. lto3 show' tically forms of apparatus which posed by heating totemperatures 'above, about 90? 0., and preferably above about 110 0. However, it the decomposition'is conducted in accordance with the prior practice, as by boiling the material in a pot-to which is attached a; spray trap,- or iractionating column, there is a gradual accumulation of tarry material in the pot which 4 makes stoppage and cleaning frequently necessary. In addition the loss oil diolenn occasionally is excessive, dueto various causes such as polymerization and/or polysillphone formation in the pot or column. 1

As an example of the amount of high-boiling tarry products formed when the monosulphone decomposition is-carriedout betchwise in a pct 00 g. o! monosulphone made by tion (1. e. the mixture of monosulphone and a small amount of polysulphone was commingled with water to dissolve the monosulphone'. the aqueous monosulphone' solution separated from the undissolved poly'sulpho ne-and then treated to separate the moncsulphone trom the water 0! may be used in carrying out the present-inven-- tion, Fig. 1 showing equipment particularly adapted for carrying out the process wherein the extent of monosulphone decomposition per pass through the decomposition acne is limited, and 1 133.2 and 3 showing equipment for use in carrying out a modified form of the process wherein a carrierisused.

In accordance with the present invention the monosulphone, preferably essentially pure, is decomposed by continuously in liquid form through a closed elongated heated zone 01' restricted cross-section, such as a tube. Preierably in the forrn 01' a coil, as a tubestill or pipestill heater of the radiant type. in which it is brought to and maintaincdata temperature suiilclently elevated sndvior a period of time suincientlyprolongcd to eil'ectv decomposition oi a substantial proportion of the monosulphone.

- The decomposition mixture is continuously removed iromthe exitendoi' the reaction soneat aratewilicienttomaintaineonstantpzessure .in the reaction zone. Preferably the reaction solution) wasplacedinadistillationflask. Heat' wasappliedtothebottomoitheilaskandthe monosulphonedecomposedoveraperiodotabout two-hoursat 10c an 120' O. attheendoithlltimeevclutlonorpiperylens zone is maintained at suhstan i atmospheric pressure as'by allowing tree flowing-onto! the reaction mixture as formed as it reach! the exit end'sothattheonlypressureisthatduetothe reslstance-to-flow inxhe tube. I

,Weh'av'e ioimdthatbycontinuouslypassing thsmonosulphonethroughareactiontubeinthe' tarrymaterial formediscarrisdalongwiththe reaction products and deposited outside the reaction tube that continuous operation is made possible without the inconvenience and expense of frequent stoppage and cleaning of the reaction zone.

- We have further found that deposition or tarry and other products may be still more effectively avoided by either or both of two procedures as follows: (1) By adjusting contact time and temperature so that the sulphone is not completely decomposed in one passage through the decomposition zone. Apparently the undecomposed monosulphone functions to continuously carry any tarry or other material from the reaction tube to a point outside where it can be conveniently (2) By providing a carrier which is passed through the decomposition zone with the sulphone. The carrier should be one which is liquid at ordinary or moderately elevated temperatures so that it may be emulsified with the liquid monosulphone. It should be liquid well below the decomposition temperature maintained in me reacton tube and should remain at least partly in the liquid form at the temperatures and moderate pressures encountered in the decomposition acne. It should be stable and not decompose at the temperatures encountered. It should be inert with respect to the materials with which it eomes into contact. It is preferably substantially immiscible with and a non-solvent for the liquid monosulphone. It should be a solvent for any tarry material or die like undedrable material which might tend to clog the reaction tube. It may be a solvent for the dioledln formedbut is preferably a non-solvent for sulphur dioxide. A high-boiling mineral oil such as gas oil, mineral seal oil. and the like is preferred. Examples of other suitable carriers are beta. beta-dichloridethylether, diphenyl, diphenyl oxide. etc. Suitable paramnic, aromatic, or naphthenic liquids may also be used. p

when using either of the foregoin procedures, the tarry and other products of low volatility remain either in solution or suspension in the liquid products leaving the decomposition sons, and may be scvar tedfromrecycle'stockinanyconvenlent manner.

undesirable polymerisation and other reactions whichresultinthelossofdioleflnsmaybeminimiled by effecting the decomposition at low pressure sayatnotaboveabomtwo atmospheres and preferably as near atmospheric as pouible. or by the presence of an inert gaseous diluent such as steam, oxygen-free flue gas, methane, ethane, propane or other hydrocarbons or the like in the reaetionaone,orbyrapidcoolingoftheproducts of decomposition to a point below that at which re-action or dioleiin polymerisation might occur. If desired, a polymerisation inhibitor, preferably non-volatile, may also be present, being introduced before the monosulphone has begun to decompose and being separated from the reagetgm products in any suitable manner and recy Use of an inert gaseous diluent is especiallydesirable because it serves to dilute the gaseous reaction products, diolenn and sulphur dioxide, as fast as formed and thereby minimise re-reaction.

Where steam is used as the diluent, a convenient mode of operation is to form it in the decomposition zone by introducing liquid water in 7 the infed material. For example instead of liquid anhydrous monosulphone we may introduce an aqueous solution of the monosulphone at room or moderately elevated temperature. Since the reaction temperature is 100 C. or above this water is converted to steam which acts as a diluent for the. reaction products.

Where an aqueous monosulphone solution is employed, it should be thoroughly intermixed with the carrier liquid, which is usually waterimmiscible, to form an intimate aqueous emulsion for introduction to the decomposition tube.

The monosulphone, with or without a diluent and/or liquid carrier, is introduced to the reaction tube under sufficient pressure to overcome the resistance thereof. The reaction tube is maintained throughout at a substantially constsnt temperature: say between about 100' C.

and about 400 C. and preferably between about 150 C. and about 250' C., in any suitable manner as by liquid or fluidiiacketing, electrical jacketing, or immersion in a suitable heating medium such as a body of liquid or gas at the desired temperature or at the transition temperature, or by use of a suitable heating furnace or zone in which fuel is burned or steam iniected,

The time of passage through the reaction tube is preferably such that at least about of the incoming monosulphone is decomposed per pass. Where procedure (1) above is used the-upper limit is desirably about The time of maintenance at the decompodtion temperature "if desired, from the carrier liquid. The monosulphone is preferably purified and recycled. The

products are then treated to separately recover the dioleiin and the sulphur dioxide. Generally this is effected by extraction of the decomposition mixture, free from monosulphone and tar. with a paraflinic liquid absorbing medium which has a boiling-point suiliciently above that of the dioleiin to enable separation therefrom by ordinary fractionation, which is a good solvent for the dioleiin, and substantially a non-solvent for sulphur dioxide. Examples of suitable liquids are high-boiling mineral oil such as paraiiin. oil, mineral seal oil, gas oil, or the like. This feature of ourinventionismorefullydisclosedintheco- I pending application of one of us, Serial No. 423,-"

535, filed December 18, 1041.

Where a diluent gas is present, it goes along with and dilutes the sulphur dioxide recovered, so that separation of sulphur dioxide by condensation or other suitable means is required before the diluent gas can be recycled. Where the diluent is steam. it may be separated from the reaction mixture by condensation as water which will usually be saturated with sulphur dioxide.

Whemthesameliquidmediumisusedasthe carrier and as the diolefln extraction medium;

such as gas oil, mineral seal oil, etc., separation of the carrier from the reaction mixture before ntering the extraction acne is optional. In case separation of carriers is dispensed with, a portion of the stripped absorption medium may be recycled to act as carrier. Where different liquids 'duced to the system via pipe I.

sulphone being decomposed.

are used for the functions of carrier and absorption medium, separation of the carrier before entering the extraction zone is usually essential. In either event, stripping of the decomposition products from the carrier may be practiced and the stripped carrier liquid recycled, thus being kept entirely separate from the diolefln abosrption medium. Usually the thus recycled carrier liquid will be in admixture with any undecomposed monosulphone.

In the reaction tube the flow may be either streamline or turbulent, preferably the latter because of more rapid reaction and less side reactions. The adjustment of the necessary factors to give either streamline or turbulent flow is well within the skill of. the art. Preferably the reaction tubeis free from any restrictions whatever, such as packing, catalyst, bafiles, etc.

Referringto Fig. l, the monosulphone is intro- If desired, a diluent such as steam, methane, ethane, oxygenfree flue gas, or the like, may be introduced through pipe 2. The sulphone,.in liquid form, with or without the diluent gas. passes through the heated reaction zone 3 which'takes the form of a tubular coil surrounded by any suitable heating means 3A for maintaining the desired temperature. The temperature maintained 'in the reaction zone may be in the range of from about 100 to about 400 C., and. preferably in the range of from about 150 to about 250 C. The heatin time is adjusted so that at least about 30% but not more than about 90% of the sulphone is decomposed ln passing through the heating zone 3.

The exact value of the heating time varies widely with the temperature maintained in the decomposition zone, varying inversely therewith, and varying to a lesser extent with the particular Thus piperylene monosulphone decomposes at a somewhat faster rate than the sulphones of butadiene or isoprene at the same temperature. The duration of the heating may range from as long as 400 minutes at 100 C. to a second or less at 250 to 300 C.

From reaction zone. 3. the reaction mixture passes to heat exchanger 4 where the temperature of the mixture is so adjusted that the unde omposed sulphone, containing only limited. amounts by allowing insoluble materials'to settle out. or through the use of selective solvents. Dissolved sulphur dioxide and similarly readily volatile material may be removed by distillation if desired. The lines l0 and II are indicated for conveying gaseous and solid or high-boiling impurities, respectively, from the unit l2. Polysulohone of either of the aliphatic conjugated dioleiins or of cyclopentadiene are quite heat-stable and may be separated out in solid form in unit l2 by suitable precipitation procedure. The purified undecomposed monosulphone is then recycled via line H to the stream of fresh monosulphone entering the decomposition tube 3.

If desired, unit I! may be by-passed partially or entirely by line 9. In some cases the undecomposed monosulphone phase recovered from unit 5 may be so pure that use ofunit I2 may be dispensed with entirely.

The uncondensed products from unit 5, comis introduced via line 26.

prising mainly diolefin and sulphur dioxide together with diluent gas it used, pass via line iv to cooler l in which they may be rapidly cooled .to well below the temperature at which reaction therebetween might occur, and then pass to separator 15 where water containing dissolved sulphur dioxide separates if steam was used as the diluent in the decomposition step. Small amounts of tarry material or polymer (polysulphone or polymerized diolefin) not removed in 5 may also separate in unit l5. The'condensate is withdrawn from l5 via line II.

The uncondensed products from unit l5, which consist essentially of diolefin, sulphur dioxide and diluent if a non-condensible diluent was used in the decomposition step, leave via line l8 and may be separated into the several components in any desired manner as by fractionation, absorption and the like. We have shown an absorption step, employing a mineral oil, as for example gas oil, mineral seal oil, or the like.

The uncondensed products next are compressed by compressor l6 and then pass to absorber l9 into the top of which absorbent oil Heat may be supplied at the bottom, of the absorber by means of the reboiler coil 2|. The unabsorbed products (sulphur dioxide and diluent gas if used) leave via line 20. The enriched oil, containing dissolved diolefin, passes via line 22 to the top of stripping tower 23. Heat is applied to the bottom of tower 23 by reboiler coil 25. Steam may be introduced through line 29 to aid in the stripping if desired; also, the pressure may be diminished. The diolefin product passes through line 24 and cooler 28 to storage or further purification steps if de sired. The stripped oil is withdrawn via line 25 and after cooling in cooler 21 passes to the top of absorber l9. Oil may be withdrawn via line 30 for cleaning if desired.

' In Fig. 2, the sulphone enters via line I. Makeup oil carrier, such as gas oil, enters via line 3| combining with gas oil recycled from the oil absorption step via line 32. The gas oil and sulphone are combined and pass. together with any recycled sulphone from line l3 through pump 33 where the streams are thoroughl mixed. Thorough intermixture at this point is essential in order to insure intimate contact and formation of an emulsion which will last at least until the reaction zone is reached, since the gas oil carrier and the liquid monosulphone are immiscible. Diluent, if desired, enters the line I after mixer 33 via line 2. The combined streams then pass through reaction tube 3 where temperature and heating time are regulated to effect partial or complete decomposition of the sulphone per pass through the heating zone 3. The reaction efiiuent is cooled in exchanger 4, to a point well below the temperature at which rereaction would occur, and passes to pump lA where the pressure is raised to a value suitable for the oil absorption step, as for example to from about 20 to about pounds per square inch gauge. The products then pass to separator' 5.where any undecomposed sulphone and insoluble products are separated out. This material may be removed via line 34 or recycled via line l3 with or without partial or complete purification in unit II as before. The mixture of gas oil, diolefin and sulphur dioxide passes via line l8 to an oil absorption step as described for Fig. 1. The carrier (gas oil) may be removed before entry into the oil absorption step, stripped of dissolved diolefln, and recycled. Alternatively, where the same oil, for example gas oil, is used as a carrier and as an absorption oil, the excess stripped oil accumulating in the exhaustion or stripping step in the oil absorption end of the process may be recycled to the incoming feed to'mixing pump 33 via line 32. If desired, a portion of the gas oil may be removed from the system for cleaning via line 30, as before.

Figure 3 shows a-process wherein a carrier, e. g., gas oil, is employed, the carrier oil being kept separate from that used in the product separation step when this is done by means of oil absorption. The sulphone enters the system through pipe I, make-up gas oil enters through pipe 3|, and combines with recycled gas oil and any recycled sulphone flowing through pipe 35. The combined gas oil and sulphone are thoroughly mixed by means of pump 33. Diluent, if desired is added through pipe 2, and the combined streams Pass to the decomposition zone 3, where temperature and heating time are regulated to effect either partial or complete decomposition of the sulphone. The products from the decomposition zone are cooled in the cooler 4 and passed to stripping column 36, where the gas oil is freed of diolefins and sulphur dioxide. Heat is supplied to the bottom of this stripper by means of reboiler coil 31.

-'I'he stripped gas oil and any undecomposed .sulphone pass from the bottom of 36 through pipe 38. Any desired portion may be passed through pipe 39 to purification means not shown in the drawing to be cleaned prior to returning to the process. The remaining product may be recycled directly to the conversion zone 3 by means of line 35. The stripping may be aided in some cases by returning to 36 through pipe 43 some sulphur dioxide or other gaseous product separated at a later stage of the process. The stripped products pass through pipe 40, cooler 4|, compressor 42 to separating means 44, where the dioleiins are separated from sulphur dioxide and diluent, if this was used. Separating means 44 may be any suitable process, as for example, oil absorption, distillation and the like. Sulphur dioxide, and diluent if used, leave separation zone 44 via line from which any desired portion may be recycled to the column 33 via line 43. The pure dioleiin'is removed via line 24. a

If desired, purification means I! similar to that shown in line l3 for Figs. 1 and 2 may be Intel- This application is a division of our prior and 4 copending application, Serial No. 423,230, filed December 16, 1941.

We claim:

1. The process of decomposing monosulphone of aliphatic conjugated diolefin which comprises continuously feeding said monosulphone together with an inert gaseous diluent into the inlet end of a closed elongated zone of restricted cross section such that flow is confined to one general direction from the inlet to the outlet end thereof, continuously passing said monosulphone through said zone from the inlet to the outlet end thereof while subjecting it to a temperature sufficiently elevated and to other conditions such as to effect decomposition of said monosulphone to the diolefin and sulphur dioxide, said inert gaseous diluent minimizing polymerization and other reactions resulting in loss of diolefin in the reaction zone and preventing re-reaction therein by diluting the gaseous decomposition products as formed, and continuously removing the decomposition mixture together with tarry matter and like material formed during the decomposition from the outlet end of said zone.

2. The process of decomposing monosulphone of aliphatic conjugated diolefin which comprises continuously feeding said monosulphone together with steam into the inlet end of a closed elongated zone of restricted cross section such that flow is confined to one general direction from the inlet to the outlet end thereof, continuously passing said monosulphone and steam through said zone from the inlet to the outlet end thereof while subjecting it to a temperature sufficiently elevated and to other conditions such asto effect decomposition of said monosulphone to the diolefin and sulphur dioxide, said steam functioning as an inert gaseous diluent minimizing polymerization and other reactions resulting in loss of diolefin in the reaction zone and preventing re-reaction by diluting the gaseous decomposition products as formed, and continuously removing the decomposition mixture together with tarry matter and like material formed during the decomposition from the outlet end of said zone.

3. The process of decomposing monosulphone of aliphatic conjugated diolefin which comprises continuously feeding an aqueous solution of said monosulphone into the inlet end of a closed elongated heated zone of restricted cross section such that flow is confined to one general direction from the inlet to the outlet end thereof, continuously posed in line 35 for purifying recycled gas oil 4 and monosulphone, to separate tarry materials or the like before recycling thereof.

It will be understood that our invention is caable of numerous modifications without departing from the spirit thereof, that the foregoing descrlption is for illustrative purposes only to teach those skilled in the art how to practice our invention, and that our invention is to be limited only by the language of the appended claims.

As used herein, the term "of restricted cross section means of limited cross-section, that is of cross-sectional area such that now is confined to substantially one general direction from one end thereof to the other. Generally the tube used will have an internal diameter not exceeding about 4 inches and not smaller than about onesixteenth of an inch. Usually tubes of a size such as is commonly used for hydrocarbon cracking operations will be employed.

passing solution through said zone from the inlet to the outlet end thereof while subjecting it to a temperature sufllciently elevated and to other conditions such as to simultaneously convert the water of solution to steam and to decompose said monosulphone to the diolefin and sulphur dioxide, said steam functioning as an inert gaseous diluent minimizing polymerization and other reactions resulting in loss of diolefin in the reaction zone and preventing re-reaction by diluting the gaseous decomposition products as formed, and continuously removing the decomposition mixture together with tarry matter and like material formed during the decomposition from the outlet end of said zone.

- FREDERICK E. FREY.

HAROLD J. HEPP. 

